This invention is generally directed to photoconductive imaging members containing alkoxy-bridged metallophthalocyanine dimers, and more specifically the present invention is directed to imaging members containing alkoxy-bridged metallophthalocyanine dimers of Formula 1 wherein M is a trivalent metal, or a metal in a trivalent form, and R is a structural moiety originating from the diol (HO--R--OH) used in the preparation of the dimer. ##STR2##
The present invention is directed, in embodiments, to photoresponsive, or photoconductive imaging members containing alkoxy-bridged gallium phthalocyanine dimers, reference copending application U.S. Ser. No. 239,432, the disclosure of which is totally incorporated herein by reference.
In embodiments, the alkoxy-bridged metallophthalocyanine dimers of the present invention can be selected as photogenerator pigments in layered photoresponsive imaging members. These photoresponsive imaging members may contain separate charge transport layers, such as hole transport layers. The photoresponsive imaging members with separate hole transport layers may contain hole transport molecules such as tertiary aryl amines, or hole transporting polymers. The aforementioned photoresponsive imaging members can be negatively charged when the photogenerating layer is situated between the hole transport layer and the substrate, or positively charged when the hole transport layer is situated between the photogenerating layer and the supporting substrate. The layered photoconductive imaging members can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and other printing processes wherein negatively charged or positively charged images are rendered visible with toner compositions of the appropriate charge. The imaging members containing alkoxy-bridged metallophthalocyanine dimers are sensitive in the wavelength regions of from about 500 to about 900 nanometers, therefore, diode lasers can be selected as the light source, especially diode lasers which emit light in the region of from 650 to 850 nanometers. The dimers can be prepared as illustrated in copending application U.S. Ser. No. 233,834, and which dimers are illustrated in copending application U.S. Ser. No. 239,432, the disclosures of which are totally incorporated herein by reference.
The use of certain phthalocyanine pigments, such as metal free phthalocyanine, vanadyl phthalocyanine, titanyl phthalocyanine, chloroindium phthalocyanines, and others as photogenerator materials in photoresponsive devices is known. Layered photoresponsive imaging members have been described in a number of U.S. Patents, such as U.S. Pat. No. 4,265,900, the disclosure of which is totally incorporated herein by reference, wherein there is illustrated an imaging member comprised of a photogenerating layer, and an aryl amine hole transport layer. Examples of photogenerating layer components include trigonal selenium, metal phthalocyanines, vanadyl phthalocyanines, and metal free phthalocyanines.
Complex electrophotograhic properties, such as photosensitivity, dark decay, cyclic stability and environmental stability of photoconductive members, or electrophotographic photoreceptors, are, for example, dependent on the purity of the photogenerating pigment, dopant components and amounts, morphology, crystal defects, the photogenerating pigment selected, and analytical differences in the pigments. The differences in the electrophotographical properties of a pigment, often a particular polymorph, are usually traced to the processes by which the pigment was obtained. To obtain a phthalocyanine based electrophotographic photoreceptor having high sensitivity to near infrared light, it is believed necessary to control the synthesis and purification procedures in order to obtain a material with the desired purity, as well as to prepare the pigment in the correct crystal modification.
The alkoxy-bridged metallophthalocyanine dimers of the present invention are considered novel phthalocyanine dimers (or diphthalocyanines), which have an alkoxy bridge (--O--R--O) linking the two metal atoms of the metallophthalocyanine rings. The structure between the two oxygen molecules of the bridge is determined by the diol used in the synthesis. The trivalent metal in the phthalocyanine dimer structure can be aluminum, gallium or indium, or trivalent transitional metals, such as Mn(III), Fe(III), Co(III), Ni(III), Cr(III), and the like. Photoconductive imaging members containing alkoxy-bridged metallophthalocyanine dimers of the present invention possess in embodiments excellent cycling properties when compared, for example, to Type V hydroxygallium phthalocyanine prepared from chlorogallium phthalocyanine.
Certain metallophthalocyanines containing two phthalocyanine rings in the molecule have been described in the literature. Early work by P.A. Barrett et al. in J. Chem Soc., 1717, 1936, discloses (AIPc).sub.2 O, a .mu.-oxo bridged aluminum phthalocyanine. Bis(phthalocyaninato)lanthanide(III) complexes, also described as lanthanide diphthalocyanines [L(Pc).sub.2 ] were first reported by I.S. Kirin et al. in Russ. J. Phys. Chem.(Engl Transl), 41, 251, 1967. The lutetium phthalocyanine dimer is disclosed in the literature, for example for its electrochromic properties. Phthalocyanines Properties and Applications, 1989, VCH Publishers, Inc., edited by C. C. Leznoff and A.B.P. Lever, describes a series of these materials with the corresponding original references. Diphthalocyanines of tetravalent metals, such as stanium, Sn(Pc).sub.2, and zirconium, Zr(Pc).sub.2, of the structure shown in Formula 2, have been synthesized and described by W. R. Bennet et al. in Inorg Chem., 12, 930, 1973 and J. Silver et al. in Polyhedron, 8, 1631, 1989. ##STR3##
Many halometallo- and hydroxymetallo phthalocyanines of trivalent metals, such as Al, Ga and In, are described in the prior art, for example in The Phthalocyanines, vol. I and II, F. H. Moser and A. L. Thomas, CRC Press Inc., 1983 and by J. P. Linsky et al. in Inorg. Chem. 19, 3131, 1980.
In Bull. Soc. Chim. Fr., 23 (1962), there is illustrated the preparation of chlorogallium phthalocyanine by reaction of o-cyanobenzamide with gallium chloride in the absence of solvent, and hydroxygallium phthalocyanine by dissolution of chlorogallium phthalocyanine in concentrated sulfuric acid, followed by reprecipitation in diluted aqueous ammonia. Further, there are illustrated in JPLO 1-221459 (Toyo Ink Manufacturing) processes for preparing chlorogallium phthalocyanines and hydroxygallium phthalocyanines, as well as photoreceptors for use in electrophotography. A number of hydroxygallium phthalocyanine polymorphs and processes for the preparation thereof are described in JPLO 5-263007, the disclosure of which is totally incorporated herein by reference.
More specifically, there is illustrated in JPLO 221459 a photoreceptor for use in electrophotography comprising a charge generation material and charge transport material on a conductive substrate, and charge generation material comprising one or a mixture of two or more of gallium phthalocyanine compounds which show the following intense diffraction peaks at Bragg angles (2 theta .+-.0.2.degree. ) in the X-ray diffraction spectrum,
1--6.7, 15.2, 20.5, 27.0 PA1 2--6.7, 13.7, 16.3, 20.9, 26.3 PA1 3--7.5, 9.5, 11.0, 13.5, 19.1, 20.3, 21.8, 25.8,27.1, 33.0.
In Konica Japanese 64-17066/89, there is disclosed, for example, the use of a new crystal modification of titanyl phthalocyanine (TiOPc) prepared from alpha-type TiOPc (Type II) by milling it in a sand mill with salt and polyethylene glycol. This publication also discloses that this new polymorph differs from alpha-type pigment in its light absorption and shows a maximum absorbance at 817 nanometers while the alpha-type exhibits a maximum at 830 nanometers. The Konica publication also discloses the use of this new form of TiOPc in a layered electrophotographic device having high photosensitivity at exposure radiation of 780 nanometers. Further, this new polymorph of TiOPc is also described in U.S. Pat. No. 4,898,799 and in a paper presented at the Annual Conference of Japan Hardcopy in July 1989. In this paper, this same new polymorph is referred to as Type Y, and reference is also made to Types I, II, and III as A, B, and C, respectively. Also, in U.S. Ser. No. 169,486, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of hydroxygallium phthalocyanine Type V, essentially free of chlorine, whereby a pigment precursor Type I chlorogallium phthalocyanine is prepared by reaction of gallium chloride in a solvent, such as N-methylpyrrolidone, present in an amount of from about 10 parts to about 100 parts, and preferably about 19 parts with 1,3-diiminoisoindoline (DI.sup.3) in an amount of from about 1 part to about 10 parts, and preferably about 4 parts of DI.sup.3 for each part of gallium chloride that is reacted; hydrolyzing said pigment precursor chlorogallium phthalocyanine Type I by standard methods, for example acid pasting, whereby the pigment precursor is dissolved in concentrated sulfuric acid and then reprecipitated in a solvent, such as water, or a dilute ammonia solution, for example from about 10 to about 15 percent; and subsequently treating the resulting hydrolyzed pigment hydroxygallium phthalocyanine Type I with a solvent, such as N,N-dimethylformamide, present in an amount of from about 1 volume part to about 50 volume parts and preferably about 15 volume parts for each weight part of pigment hydroxygallium phthalocyanine that is used by, for example, ball milling said Type I hydroxygallium phthalocyanine pigment in the presence of spherical glass beads, approximately 1 millimeter to 5 millimeters in diamete, at room temperature, about 25 degrees, for a period of from about 12 hours to about 1 week, and preferably about 24 hours such that there is obtained a hydroxygallium phthalocyanine Type V, ball milling contains very low levels of residual chlorine of from about 0.001 percent to about 0.1 percent, and in an embodiment about 0.03 percent of the weight of the Type V hydroxygallium photogenerating pigment, as determined by elemental analysis.
Further, in U.S. Ser. No. 169,900, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of photogenerating hydroxygallium phthalocyanine Type V, which comprises formation of a precursor of gallium phthalocyanine, prepared by reaction of 1,3-diiminoisoindoline with gallium acetylacetonate in a suitable solvent solvent; hydrolyzing the precursor by dissolving in a strong acid and then reprecipitating the dissolved pigment in aqueous ammonia, thereby forming Type I hydroxygallium phthalocyanine; and admixing the Type I hydroxygallium phthalocyanine with a polar aprotic organic solvent; and more specifically a process for the preparation of Type V hydroxy gallium phthalocyanine which comprises preparing a precursor gallium phthalocyanine, by the reaction of 1,3-diiminoisoindoline with gallium acetylacetonate in a suitable solvent; filtering and thereafter washing the pigment precursor gallium phthalocyanine with hot N,N-dimethylformamide, followed by washing with an organic solvent, such as methanol, or acetone; hydrolyzing said precursor by dissolving in a strong acid and then reprecipitating the dissolved pigment in aqueous ammonia, thereby forming Type I hydroxygallium phthalocyanine; and admixing the Type I with the organic solvent N,N-dimethylformamide.
The alkoxy-bridged metallophthalocyanine dimers of the present invention can be obtained by the reaction of ortho-phthalodinitrile or 1,3-diiminoisoindoline with a trivalent metal alkoxide in the presence of a diol. During the aforementioned reaction, the diol, which can also act as a solvent for the reaction, is chemically incorporated into the phthalocyanine product with the formation of an alkoxy-bridged metallophthalocyanine dimer of the formula C.sub.32 H.sub.16 N.sub.8 MOROMN.sub.8 H.sub.16 C.sub.32 as illustrated in Formula 1, wherein M is a trivalent metal and the alkoxy bridge (--O--R--O) contains the diol moiety (R). The alkoxy-bridged metallophthalocyanine dimers can also be obtained by the reaction of ortho-phthalodinitrile or 1,3-diiminoisoindoline with other complexes of trivalent metals, such as the acetates and acetylacetonates, in the presence of a diol. Alternatively, the alkoxy-bridged metallophthalocyanine dimers can be prepared by the reaction of hydroxy metallophthalocyanines of a trivalent metal with a diol in the presence of excess diol or another solvent. Processes for the preparation of the dimers are illustrated in copending patent applications U.S. Ser. No. 239,432, and U.S. Ser. No. 233,195, the disclosures of which are totally incorporated herein by reference.
In the following copending patent applications filed concurrently herewith there is illustrated: U.S. Ser. No. 239,432 akoxy-bridged metallophthalocyanine dimers of the formula C.sub.32 H.sub.16 N.sub.8 MOROMN.sub.8 H.sub.16 C.sub.32, or of the formula ##STR4## wherein M is a metal, and R is an alkyl or an alkyl ether; U.S. Ser. No. 233,834 a process for the preparation of Type V hydroxygallium phthalocyanine which comprises the in situ formation of an alkoxy-bridged gallium phthalocyanine dimer, hydrolyzing said alkoxy-bridged gallium phthalocyanine dimer to hydroxygallium phthalocyanine, and subsequently converting the hydroxygallium phthalocyanine product obtained to Type V hydroxygallium phthalocyanine; a process for the preparation of Type V hydroxygallium phthalocyanine which comprises the formation of an alkoxy-bridged gallium phthalocyanine dimer by the reaction of an organic gallium complex with ortho-phthalocyannine, or 1,3-diiminoisoindoline and a diol; and U.S. Ser. No. 235,195 is a process for the preparation of alkoxy-bridged metallophthalocyanine dimers by the reaction of a trivalent metal compound with ortho-phthalodinitrile or 1,3-diiminoisoindoline in the presence of a diol.
The disclosures of all of the aforementioned publications, laid open applications, copending applications and patents, are totally incorporated herein by reference.